These years in a magnetic tape used for backup of a computer and the like, high density recording is progressing and some tape has a memory capacity not less than 100 GB (Giga Bytes). Such the magnetic tape achieves an improvement of recording density by narrowing a width of a data track itself and distance between neighboring tracks to increase the number of data tracks when forming a data track along a longitudinal direction (running direction). For example, a magnetic tape cartridge according to LTO (Linear Tape Open) standard forms as many as 384 pieces of data tracks in a tape width of 12.65 mm.
Because such the magnetic tape described above is very narrow in the width of the data track and the distance between the neighboring data tracks, the magnetic tape drive is equipped with a head unit having a plurality of data signal recording heads and data signal reproducing heads narrow in width. In the head unit, one data signal recording head and data signal reproducing head are in charge of recording and reproducing of plural neighboring data tracks, and the whole head unit is made to move a minute amount in a width direction of the magnetic tape with reciprocating it plural times for the head unit, thereby each data signal recording head and data signal reproducing head being moved on a neighboring data track and recording and reproducing of data tracks corresponding to their pieces being handled.
In the recording/reproduing of the magnetic tape, it is requested for the magnetic tape drive to control a position of the head unit in the width direction of the magnetic tape with a high accuracy so that each data signal recording head and data signal reproducing head accurately position on a data track to be handled. Therefore, a tracking servo technology controlling the position of the head unit in the width direction of the magnetic tape is introduced. The tracking servo technology is a technology which reads a servo signal written in the magnetic tape in advance with a servo signal reading head provided at the head unit, moves the position of the head unit in the width direction of the magnetic tape by a head unit moving device in response to the read servo signal, and accurately positions the data signal recording head and data signal reproducing head on the data track to be handled.
Incidentally, the magnetic tape drive described above adjusts the position of the head unit in the width direction of the magnetic tape by the head unit moving device, so an accuracy positioning the head unit depends on the moving device and a responsivity of its peripheral circuit. Then, conventionally a pseudo signal is input in the head unit moving device and peripheral circuit, and a moved amount of the head unit moved in response to the pseudo signal is measured with an optical sensor and the like, thereby the responsivities of the moving device and peripheral circuit are inspected. Meanwhile, as a conventional technology purposing an improvement of a device responsivity, for example, there exists an “Information Reproducing Apparatus” disclosed in Japan patent laid open 110986.